Coordinate measuring machine having a non-sensing probe

ABSTRACT

A coordinate measuring machine including a support platform for supporting an object. Scanning means is supported by the support platform. The scanning means includes a probe assembly and a non-contact scanner. Drive means is connected to at least one of the probe assembly and the non-contact scanner for moving the probe assembly and non-contact scanner relative to each other. The probe assembly includes a probe movably disposed in a guide tube. The probe includes a shaft and a tip integrally formed from either a fiber-optic or non-fiber-optic material. The tip extends from the guide tube so as to be detectable by the non-contact scanner. The tip may include one or more stylus. During operation the tip contacts the object and the non-contact scanner detects the tip to determine the corresponding coordinates of the object. A light source illuminates the tip for improved detection of the tip. When the probe is formed of a fiber-optic material, light is emitted through the probe. When the probe is formed of a non-fiber-optic material, light is emitted through a fiber-optic ring disposed in the guide tube and surrounding the shaft. Dislodging means dislodges the tip from the object reducing the build up of static forces between the tip and the object. Cleaning means removes foreign particles from the tip. In the event that the tip breaks from the shaft, feeding means advances the shaft exposing the shaft to heating means. The heating means heats the corresponding the shaft to form a new tip.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of the U.S. patent application Ser. No.09/335,211 filed Jun. 17, 1999, that issued as the U.S. Pat. No.6,240,651 on Jun. 5, 2001 which claims the benefit of provisionalapplication No. 60/105,109 filed Oct. 21, 1998.

BACKGROUND OF THE INVENTION

This invention relates in general to a coordinate measuring machine.More specifically, this invention relates to a coordinate measuringmachine having an image processor and a probe detectable by the imageprocessor.

Conventional coordinate measuring machines used in measuring an objecttypically include a sensing probe mounted to a moveable spindle. Thesensing probe includes a shaft interconnecting a sensor and a contacttip. In making a measurement, the spindle positions the probe to wherethe contact tip contacts the object, which causes the sensor to deflect.The sensor may be a measuring type sensor or a switching type sensor.The measuring type sensor measures displacement as a function of thedeflection of the sensor, whereas the switching type sensor generates aswitching signal upon the sensor deflecting a predetermined amount. Theshaft of either sensing type probe must be sufficiently rigid totransmit the loading force on the contact tip to the sensor. However,this rigidity requirement places a limit on how small the shaft andcontact tip can be, which in turn restricts how small of a measurementcan be taken.

Various coordinate measuring machines having non-contact sensors, suchas image processors and/or lasers, have been proposed that are capableof taking smaller measurements than a typical sensing probe. However,the non-contact sensors are not as well suited as a probe for makingcertain type measurements, such as measuring the internal surface of acylinder.

Still other coordinate measuring machines having an image processor anda flexible non-sensing probe have been proposed. The image processor andnon-sensing probe are arranged on a single spindle in a manner such thatthe non-sensing probe is detectable by the image processor. In making ameasurement, the image processor detects the position of the non-sensingprobe when the non-sensing probe is placed in contact with the intendedmeasurement object. The non-sensing probe includes a shaft and contacttip integrally formed from a fiber-optic material. Because the shaft ofthe non-sensing probe need not exhibit load transfer capabilities, thesize of non-sensing probe can be relatively small as compared to atypical sensing probe. Consequently, a coordinate measurement machineutilizing an image processor and non-sensing probe combination iscapable of making smaller contact measurements than can a coordinatemeasurement machine utilizing a typical sensing probe. However, due tothe brittle nature of the non-sensing probe, the shaft of thenon-sensing probe is susceptible to breaking under normal useconditions. Consequently, the non-sensing probe may have to be replaceda number of times during the normal course of a measurement process. Inreplacing the non-sensing probe, the contact tip portion of thenon-sensing probe must be positioned in the focus plane of the camera.The replacement of probe typically requires at least some form of manualsupport. Consequently, these types of machines generally cannot operatefor lengthy periods of time without the need for operator assistance.

Another concern associated with the non-sensing probe is the build up ofstatic forces between the contact tip portion of the non-sensing probeand the measurement object, which cause the contact tip to cling to themeasurement object. This clinging phenomenon may cause the contact tipto break from the probe when attempting to separate the probe from theobject.

Additionally, dust or other particles may stick to the contact tip,which may cause inaccuracies in the measurements taken.

Furthermore, because the non-sensing probe and image processor aremounted to a common spindle in a “fixed” relationship relative to oneand other, it is difficult to hold the contact tip portion in focus whenplacing the contact tip in contact with the object. Also, it may bedesirable to operate the image processor independent of the non-sensingprobe when in making certain measurements. However, in order for theimage processor to directly make a measurement of an object, thenon-sensing probe must be removed from the spindle. The removal and thesubsequent replacement of the non-sensing probe from and to the spindleadd to the time and cost of the measurement operation.

One objective of this invention is to provide means for automaticallyrepairing the non-sensing probe. Another objective of this invention isto provide means for cleaning the non-sensing probe. Additionally, it isan objective of this invention to provide means for dislodging thenon-sensing probe from a measurement object. Furthermore, it is anobjective of this invention to provide means for moving the non-sensingprobe and image processor relative to one and other. Still further, itis an objective of this invention to reduce the likelihood of damage tothe non-sensing probe while maintaining detection of the non-sensingprobe by the image processor.

SUMMARY OF THE INVENTION

This invention concerns a coordinate measuring machine for measuring anobject. The machine comprises a support platform for supporting theobject. A non-contact scanner and a probe detectable by the non-contactscanner are supported by the support platform. The probe includes ashaft having a contact end portion. The contact end portion includes atip for contacting the object. The tip may include at least one stylusfor contacting the object.

The machine may further comprise heating means proximate the supportplatform for forming the tip by heat transferred from the heating meansto the contact end portion.

Additionally, the machine may comprise cleaning means proximate thesupport platform for cleaning the tip.

Also, the machine may comprise dislodging means proximate the tip fordislodging the tip from the object.

Furthermore, the machine may comprise drive means connected to at leastone of the non-contact scanner and the probe for moving the non-contactscanner and the probe relative to one and other.

The machine may also comprise a fiber-optic ring adapted for receivinglight from a light source and proximate the probe for illuminating thetip, which better enables the non-contact scanner to detect the tip.

Preferably the probe is formed of a fiber-optic material. Alternatively,the probe may be formed of a suitable non-fiber-optic material.

Various objects and advantages of this invention will become apparent tothose skilled in the art from the following detailed description of thepreferred embodiments, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a coordinate measuring machine accordingto this invention;

FIG. 2 is an enlarged sectional view of a portion of the probe assemblyshown in FIG. 1.;

FIG. 3 is an enlarged sectional view of a portion of the probe assemblyshown in FIG. 1 illustrating the relationship between the probe assemblyand the heating means shown in FIG. 1 when forming a tip of the probeassembly;

FIG. 4 is an enlarged sectional view of a portion of the probe assemblyillustrating a compressed air source in communication with the probeassembly;

FIG. 5 is an enlarged sectional view of the portion of a probe assemblyshown in FIG. 1 illustrating the relationship between the probe assemblyand a rinsing bath when cleaning the tip of the probe assembly; and

FIG. 6 is an enlaged sectional view of a portion of the probe assemblyshown in FIG. 1 illustrating the relationship between the light sourceshown in FIG. 1 and assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A coordinate measuring machine according to this invention is showngenerally at 10 in FIG. 1. The machine 10 comprises a support platformindicated generally at 12. The support platform 12 includes a base 14having a flat surface 16 for mounting an object to be measured.Preferably, the flat surface 16 is positioned horizontally. Each of twoopposing pillars 18 extends upwardly from a common side of the base 14.Each pillar 18 is perpendicular to the base 14. A cross-member 20,presenting a longitudinal axis or X-axis, interconnects the pillars 18at upper ends.

The machine 10 further comprises a cross-carrier 22 presenting alongitudinal axis or Y-axis perpendicular to the X-axis. One end of thecross-carrier is movably mounted to the cross-member 20 for movementparallel to the X-axis. A post 24 extending downwardly from the otherend of the cross-carrier 22 is movably supported in a guide track 26formed in the base 14 parallel to the cross-member 20 for movementparallel to the X-axis.

The probe assembly 34 includes a probe holder 36 having a proximal endremovably mounted to the probe spindle 32. Preferably, the proximal endof the probe holder 36 is of a well-known configuration such that theprobe holder 36 can be placed in a standard probe changer (not shown),such a RENISHAW® probe changer, when the probe assembly 34 is not inuse. The probe assembly 34 further includes a guide tube 38 having aproximal end attached to a distal end of the probe holder 36. The guidetube is generally L-shape with a portion of the guide tube 38 adjacentthe proximal end of the guide tube 38 being held in a generallyhorizontal orientation, and an adjoining portion of the guide tube 38being turned downward. A probe 40 is disposed in and extends from theguide tube 38.

FIG. 2 shows a portion of the probe assembly 34 in greater detail. Theprobe, indicated generally at 40, includes a shaft 42 having a supplyportion 44 and a contact end portion 46. The supply portion 44 ismovably disposed in the guide tube 38 with the contact end portion 46extending from a distal end of the guide tube 38. In addition tosupporting the probe 40, the guide tube 38 acts as supply means forstoring the supply portion 44, the importance of which will be discussedbelow. A tip 48 is integrally formed from the contact end portion 46 forcontacting a measurement object 50. Preferably, the probe 40 is formedof a fiber-optic material, such as glass. Alternatively, the probe 40may be formed of any suitable material such as plastic, metal or thelike. The length of the guide tube 38 is such that the tip 48 ispositioned so as to be detectable by the image processor 31. The tip 48is preferably spherical, but may be any shape recognizable by the imageprocessor 31, such as disc-shaped, conical or the like. Additionally,the tip 48 may include one or more stylus 52 (two shown) for increasingthe measuring sensitivity capability of the probe 40. In order for thetip 48 to be detectable by the image processor, the shaft 42 has amaximum shaft area perpendicular to the longitudinal axis of the shaft42 less than a maximum tip area of the tip 48 parallel to the maximumshaft area.

The probe assembly 34 may further include feeding means 49 of anywell-known type for incrementally advancing the supply portion 44 of theshaft 42 toward the proximal end of the guide tube 38. The feeding means49 is useful in the event that the tip 48 becomes damaged or separatedfrom the shaft 42. The operation of the feeding means is discussed ingreater detail below.

FIG. 3 shows the feeding means 49 as including a pair of opposing drivewheels 54 rotatably supported relative to the guide tube 38. Preferably,one of the drive wheels 54 is adapted for connection to a suitable drivemotor or the like (not shown). Alternatively, the drive motor may driveeach of the drive wheels 54. The supply portion 44 of the shaft 42engages a portion of the perimeter of each of the drive wheels 54. Thefrictional force between the shaft 42 and the drive wheels 54 issufficient to advance the shaft 42 when the drive motor rotates thedrive wheels 54. Alternatively, the feeding means 49 may included aclamping device (not shown), screw device (not shown) or a piston device(not shown) arranged in relationship with the supply portion 44 suchthat the shaft 42 is advanced toward the proximal end of the guide tube38 upon actuation of the associated clamping device, screw device orpiston device.

The probe assembly 34 may further include supply means for storing aportion of the supply portion 44 of the shaft 42 that exceeds the lengthof the guide tube 38, such as a spool 56 rotatably supported relative tothe guide tube 38 as shown in FIG. 3.

Referring to FIGS. 1 and 3, the machine 10 further comprises heatingmeans 58 for forming the tip from the contact end portion of the shaft.Preferably, the heating means 58 includes any well-known radiant heatsource (not shown) for transferring heat to the contact end portion 46.The heating means 58 is supported by or relative to the support platform12 such that the contact end portion 46 can be positioned proximate tothe heating means 58. The heating means 58 may further include a heatedmold (not shown), shaped consistent with the desired shape of the tip48, for transferring heat to the contact end portion 46 when placed incontact with the contact end portion 46.

Additionally, the machine 10 may include cutting means 59, as shown inFIG. 3, of a well-known type such as a scissor-like device (not shown)for cutting the shaft 42 adjacent to the proximal end of the guide tube38. The cutting means 59 is illustrated as being mounted relative to thesupport platform 12, but may be made part of the probe assembly 34. Theshaft 42 may be cut either prior to or after the feeding means 49advances the shaft 42 but prior to forming the tip 48. The purpose forcutting the shaft 42 is to position the contact end portion 44 apredetermined distance from the heating means 58 when forming the tip48.

Referring to FIGS. 1 and 4, the machine 10 may further includedislodging means 60 for dislodging the tip 48 from a measurement object.Preferably, the dislodging means 60 includes a compressed air source 61placed in fluid communication with the guide tube 38.

Referring to FIGS. 1 and 5, the machine 10 may further include cleaningmeans 62 for removing dust or other particulate from the tip 48 betweenmeasurements. Preferably, the cleaning means 62 includes a rinsing bath63 supported by or placed relative to the support platform 12 such thatthe tip 48 can be placed in the rinsing bath 63. The rinsing bath 63 isfilled with any well-known rinsing agent 64. The cleaning means 62 mayfurther include agitation means 66 for agitating the rinsing agent 64.Preferably, the agitation means 66 includes a pair of ultrasonic pulsegenerators 67 mounted to opposite sides of the rinsing bath 63, but mayinclude any well-known mechanical agitator (not shown).

Referring to FIG. 1 the machine 10 may further include a suitable lightsource 68 for illuminating the tip 48, which better enables the imageprocessor 31 to detect the tip 48. When the probe 40 is a fiber-opticmaterial, the light source 68 is preferably configured in a manner so asto emit light through the shaft 42 and tip 48.

Referring to FIGS. 1 and 6, when the probe 40 is a non-fiber-opticmaterial, the light source 68 is arranged in relationship to the guidetube 38 so as to emit light into an opening of the guide tube 38adjacent the proximal end of the guide tube 38. Regarding thisarrangement, the probe assembly 34 further includes a fiber-optic ringor sleeve 70 surrounding the portion of the shaft 42 disposed in theguide tube 38. In this arrangement, the light source 68 emits light thatpasses through the ring 70. The ring 70 in turn emits light on the tip48. A possible advantage of making the probe 40 from a non-fiber-opticis that a material may be chosen which is less brittle and/or strongerthan a fiber-optic material. Accordingly, the probe 40 may be lesssusceptible to breaking.

Referring to FIG. 1, the machine 10 further includes a control unit 72connected to drive motors (not shown) for driving the movement of thecross-carrier 22, the carriage 28 and the spindles 30 and 32. Thecontrol unit 72 is also connected to the image processor 31, the cuttingmeans 59, the heating means 58, the dislodging means 60 and the cleaningmeans 62 for controlling the various functions of each of theseelements. The control unit 72 is of a well-known type. Preferably, thecontrol unit 72 includes a computer (not shown). An input panel (notshown), a monitor (not shown), and a printer (not shown) are eachconnected to the computer.

In operation, the control unit 72 selectively actuates the drive motorsconnected to the cross-carrier 22, the carriage 28 and the probe spindle32, which in turn cause the tip 48 to placed in contact with the givenobject. The control unit 72 then actuates the drive motor connected tothe scanner spindle 30 so that the image processor 31 is properlyfocused on the tip 48. The coordinates of tip 48 are then computed byuse of a best-fit algorithm. This process is may be repeated a number oftimes for a given object.

During the measurement of a given object, static attractive forces maybuild up between the tip 48 and the given object. In the event that thestatic force between the tip 48 and the given object become greater thanthe strength of the shaft 42, the shaft 42 will break upon attempting toseparate the tip 48 from the given object. In order to counter act thebuild up of the static forces, compressed air is released after eachmeasurement from the compressed air source 61 into the guide tube 38.The guide tube directs the air 38 across the top and along the sides ofthe tip 48 dislodging the tip 48 from the given object. By directing theair in this manner, the tip 48 can be separated from the given objectwithout dragging the tip 48 along the given object. Thus, the build upof the static forces is controlled.

In addition to dislodging the tip 48 from the given object, thecompressed air directed by the guide tube 38 also has the effect ofremoving dust or other particles from the tip 48. Thus, the accuracy ofsubsequent measurements can be maintained.

As an alternative to cleaning the tip 48 with compressed air, the tip 48can be placed in the rinsing bath 62 by selective movement of thecross-carrier 22, carriage 28 and probe spindle 32. This operation maybe programmed to occur as often as necessary. In addition, thisoperation may have the effect of reducing the build up of the staticcharge on the tip 48.

In the event that the tip 48 becomes damaged or breaks off the shaft 42,the probe 40 can be automatically repaired. The image processor 31 firstsignals the control unit 72 that the tip 48 cannot be properly focused.In turn, the control unit 72 commands the actuation of the cutting means59. In turn, the cutting means 59 cuts the shaft 42 adjacent to theproximal end of the guide tube 38. The drive wheels 54, or the like, arecommanded to advance the supply portion 44 of the shaft 42 a prescribedamount. The control unit 72 then selectively commands the drive motorsconnected to the cross-carrier 22, carriage 28 and probe spindle 32 toposition the contact end portion 46 of the shaft 42 in a prescribedorientation with respect to the heating means 58. The heating means 58is then automatically energized for a prescribed period of time, duringwhich the contact end portion 46 is melted so as to form the tip 48.

As can be appreciated, the base 14 of the machine 10 can be arranged soas to be movable in addition to or in substitution to the movement ofthe cross-carrier 22, carriage 28 and/or one of the spindles 30, 32. Inother words, the object 50, the cleaning means 66, the cutting means 59and the heating means 58 can be moved to the probe 40 in combinationwith or in place of the probe 40 being moved.

In accordance with the provisions of the patent statutes, the principleand mode of operation of this invention have been explained andillustrated in its preferred embodiments. However, it must be understoodthat this invention may be practiced otherwise than as specificallyexplained and illustrated without departing from its spirit or scope.

What is claimed is:
 1. A coordinate measuring machine for measuring anobject comprising: a support platform for supporting the object; a probesupported by said support platform, said probe including a tip forcontacting the object; and cleaning means proximate said supportplatform for cleaning said tip when not in contact with the object, saidcleaning means selectively providing each of liquid and gaseous cleaningagents to said tip, said cleaning means including a compressed airsource in fluid communication with said tip whereby particulate isremoved from said tip by said gaseous cleaning agent as air is suppliedfrom said compressed air source, said cleaning means further including aguide tube, said compressed air source being connected in fluidcommunication with one end of said guide tube, said probe being disposedin said guide tube with said tip extending from another end of saidguide tube and said air exiting said guide tube from said another end.2. A coordinate measuring machine for measuring an object comprising: asupport platform for supporting the object; a probe supported by saidsupport platform, said probe including a tip for contacting the object;and cleaning means proximate said support platform for cleaning said tipwhen not in contact with the object, said cleaning means selectivelyproviding each of liquid and gaseous cleaning agents to said tip; anddrive means connected to at least one of said probe and said cleaningmeans for moving said probe and said cleaning means relative to oneanother whereby said tip and said cleaning means are positionedproximate each other when cleaning said tip with said cleaning means. 3.The machine according to claim 2 wherein said cleaning means includes arinsing bath having said liquid cleaning agent as a rinsing agentdisposed in said rinsing bath, said probe and cleaning means beingrelatively positioned by said drive means to submerse said tip in saidrinsing agent when cleaning said tip with said cleaning means.
 4. Themachine according to claim 3 wherein said cleaning means includesagitation means for agitating said rinsing agent.
 5. A coordinatemeasuring machine for measuring an object comprising: a support platformfor supporting the object; a probe supported by said support platform,said probe including a tip for contacting the object; and dislodgingmeans proximate said tip for dislodging said tip from the object whensaid tip is attracted to the object by static attractive force, saiddislodging means acting to dislodge said tip from contact with theobject prior to moving said probe relative to the object.
 6. The machineaccording to claim 5 wherein said dislodging means includes a compressedair source in fluid communication with said tip whereby dust and otherparticles are removed from said tip by compressed air supplied from saidcompressed air source.
 7. The machine according to claim 6 wherein saiddislodging means includes a guide tube supported by said supportplatform, said compressed air source being connected in fluidcommunication one end of said guide tube, said probe being disposed insaid guide tube with said tip extending from another end of said guidetube whereby compressed air supplied by said compressed air source isfed through said guide tube and exits at said another end to flow acrosssaid tip.